Brake Fluid Pump: Description and Operation

The electric pump fills the hydraulic accumulator with fluid under high pressure The pump mounts to the hydraulic unit, using insulators. Fluid from the reservoir is delivered to a passage between the hydraulic accumulator and the booster control valve. A contact switch operated by the hydraulic pressure of the accumulator controls the operation of the pump electrical motor. The switch contacts are part of the pump relay control circuit When the ignition switch is in the "run" position, the pump motor will run if the pressure switch is closed. The contacts will:
^ Close when accumulator pressure drops below 14,000 kPa (2030 psi)
^ Open when accumulator pressure rises above 18,000 kPa (2610 psi) The pump contains a pressure relief valve that opens at 23,030 kPa (3340 psi). Fluid pressure is relieved to the reservoir if the pump continues to run after the pressure switch opens. The pressure switch contacts for the "BRAKE" warning lamp circuit will close when pressure drops below 10,343 kPa (1500 psi). The contacts will open when pressure rises above 13,100 kPa (1900 psi). The pressure switch also contains contacts for an EBCM circuit, which affect the operation of the "ANTILOCK" warning lamp. These contacts operate at the same hydraulic accumulator pressures as those in the "BRAKE" warning lamp circuit, but open rather than close with low pressure. The contacts will close as pressure rises.